Gallium and nitrogen containing laser device having confinement region

ABSTRACT

A method for fabricating a laser diode device includes providing a gallium and nitrogen containing substrate member having a surface region, forming a patterned dielectric material overlying the surface region to expose a portion of the surface region within a vicinity of an recessed region of the patterned dielectric material and maintaining an upper portion of the patterned dielectric material overlying covered portions of the surface region, and performing a lateral epitaxial growth overlying the exposed portion of the surface region to fill the recessed region and causing a thickness of the lateral epitaxial growth to be formed overlying the upper portion of the patterned dielectric material. The method also includes forming an n-type gallium and nitrogen containing material, forming an active region, and forming a p-type gallium and nitrogen containing material. The method further includes forming a waveguide structure in the p-type gallium and nitrogen containing material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/480,398, filed Sep. 8, 2014, which claims priority to U.S. Ser. No.61/892,981, filed Oct. 18, 2013, both of which are commonly assigned andhereby incorporated by reference herein.

BACKGROUND

In 1960, the laser was first demonstrated by Theodore H. Maiman atHughes Research Laboratories in Malibu. This laser utilized asolid-state flashlamp-pumped synthetic ruby crystal to produce red laserlight at 694 nm. By 1964, blue and green laser output was demonstratedby William Bridges at Hughes Aircraft utilizing a gas laser designcalled an Argon ion laser. The Ar-ion laser utilized a noble gas as theactive medium and produce laser light output in the UV, blue, and greenwavelengths including 351 nm, 454.6 nm, 457.9 nm, 465.8 nm, 476.5 nm,488.0 nm, 496.5 nm, 501.7 nm, 514.5 nm, and 528.7 nm. The Ar-ion laserhad the benefit of producing highly directional and focusable light witha narrow spectral output, but the wall plug efficiency was <0.1%, andthe size, weight, and cost of the lasers were undesirable as well.

As laser technology evolved, more efficient lamp pumped solid statelaser designs were developed for the red and infrared wavelengths, butthese technologies remained a challenge for blue and green and bluelasers. As a result, lamp pumped solid state lasers were developed inthe infrared, and the output wavelength was converted to the visibleusing specialty crystals with nonlinear optical properties. A green lamppumped solid state laser had 3 stages: electricity powers lamp, lampexcites gain crystal which lases at 1064 nm, 1064 nm goes into frequencyconversion crystal which converts to visible 532 nm. The resulting greenand blue lasers were called “lamped pumped solid state lasers withsecond harmonic generation” (LPSS with SHG) had wall plug efficiency of˜1%, and were more efficient than Ar-ion gas lasers, but were still tooinefficient, large, expensive, fragile for broad deployment outside ofspecialty scientific and medical applications. Additionally, the gaincrystal used in the solid state lasers typically had energy storageproperties which made the lasers difficult to modulate at high speedswhich limited its broader deployment.

To improve the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized to replace the inefficient andfragile lamps. These “diode pumped solid state lasers with SHG” (DPSSwith SHG) had 3 stages: electricity powers 808 nm diode laser, 808 nmexcites gain crystal which lases at 1064 nm, 1064 nm goes into frequencyconversion crystal which converts to visible 532 nm. The DPSS lasertechnology extended the life and improved the wall plug efficiency ofthe LPSS lasers to 5%-10%, and further commercialization ensue into morehigh-end specialty industrial, medical, and scientific applications.However, the change to diode pumping increased the system cost andrequired precise temperature controls, leaving the laser withsubstantial size, power consumption while not addressing the energystorage properties which made the lasers difficult to modulate at highspeeds.

As high power laser diodes evolved and new specialty SHG crystals weredeveloped, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser operating withlongitudinal mode (single frequency) and single spatial mode, 1064 nmgoes into frequency conversion crystal, which converts to visible 532 nmgreen light. These lasers designs are meant to improve the efficiency,cost and size compared to DPSS-SHG lasers, but the specialty single modediodes, high precision laser beam alignment, and crystals required makethis challenging today. Additionally, while the diode-SHG lasers havethe benefit of being directly modulate-able, they suffer from severesensitivity to temperature, which limits their application.

SUMMARY

The present disclosure relates generally to optical techniques. Morespecifically, the present disclosure provides methods and devices usingnonpolar, semi-polar, or polar c-plane oriented gallium and nitrogencontaining substrates for optical applications ranging in the violet,blue, and green spectral region, among others, including combinationsthereof, and the like.

In an example, the present invention provides a method for fabricating alaser diode device. The method includes providing a gallium and nitrogencontaining substrate member comprising a surface region, a releasematerial overlying the surface region, an n-type gallium and nitrogencontaining material, an active region overlying the n-type gallium andnitrogen containing material, a p-type gallium and nitrogen containingmaterial; and a first transparent conductive oxide material overlyingthe p-type gallium and nitrogen containing material, and an interfaceregion overlying the first transparent conductive oxide material. Themethod includes bonding the interface region to a handle substrate andsubjecting the release material to an energy source to initiate releaseof the gallium and nitrogen containing substrate member.

In an example, the interface region is comprised of metal, asemiconductor and/or another transparent conductive oxide. In anexample, the interface region comprises a contact material.

In an example, the energy source is selected from a light source, achemical source, a thermal source, or a mechanical source, and theircombinations. In an example, the release material is selected from asemiconductor, a metal, or a dielectric. In an example, the releasematerial is selected from GaN, InGaN, AlInGaN, or AlGaN such that theInGaN is released using PEC etching. In an example, the active regioncomprises a plurality of quantum well regions.

In an example, the method comprises forming a ridge structure configuredwith the n-type gallium and nitrogen containing material to form ann-type ridge structure, and forming a dielectric material overlying then-type gallium and nitrogen containing material, and forming a secondtransparent conductive oxide material overlying an exposed portion ofthe n-type gallium and nitrogen containing material such that activeregion is configured between the first transparent conductive oxidematerial and the second conductive oxide material to cause an opticalguiding effect within the active region. In an example, the methodincludes forming an n-type contact material overlying an exposed portionof the n-type gallium and nitrogen containing material or forming ann-type contact material overlying a conductive oxide material overlyingan exposed portion of the n-type gallium and nitrogen containingmaterial. In an example, the method includes forming an n-type contactregion overlying an exposed portion of the n-type gallium and nitrogencontaining material; forming a patterned transparent oxide regionoverlying a portion of the n-type contact region; and forming athickness of metal material overlying the patterned transparent oxideregion; wherein the p-type gallium and nitrogen containing material isconfigured as a ridge waveguide structure to form a p-type ridgestructure.

In an example, the transparent conductive oxide is comprised of indiumtin oxide or zinc oxide.

In an example, the method includes forming an n-type contact regionoverlying an exposed portion of the n-type gallium and nitrogencontaining material; forming a patterned dielectric region overlying aportion of the n-type contact region; and forming a thickness ofconformal metal material overlying the patterned dielectric region;wherein the p-type gallium and nitrogen containing material isconfigured as a ridge waveguide structure to form a p-type ridgestructure. In an example, the dielectric region is comprised of siliconoxide or silicon nitride. In an example, the method includes forming aridge waveguide region in or overlying the n-type gallium and nitrogencontaining material to form an n-type ridge structure; forming a secondconductive oxide region overlying the n-type gallium and nitrogencontaining material; and forming a metal material overlying thetransparent oxide region.

In an example, the handle substrate is selected from a semiconductor, ametal, or a dielectric or combinations thereof. In an example, thehandle substrate is selected from a silicon wafer or a gallium arsenidewafer or an indium phosphide wafer. In an example, the bondingcomprising thermal bonding, plasma activated bonding, anodic bonding,chemical bonding, or combinations thereof. In an example, the surfaceregion of the gallium and nitrogen containing substrate is configured ina semipolar, polar, or non-polar orientation.

In an example, the method further comprising forming a laser cavity isoriented in a c-direction or a projection of a c-direction and forming apair of cleaved facets using a cleave propagated through both the handlesubstrate material and the gallium and nitrogen containing material. Themethod also further comprising forming a laser cavity is oriented in ac-direction or a projection of a c-direction and forming a pair ofetched facets.

In an example, the handle substrate is an indium phosphide substratematerial; and further comprising separating a plurality of laser dice byinitiating a cleaving process on the indium phosphide substratematerial. In an example, the handle substrate is a gallium arsenidesubstrate material; and further comprising separating a plurality oflaser dice by initiating a cleaving process on the gallium arsenidesubstrate material. In an example, the method further comprisesseparating a plurality of laser dice by initiating a cleaving process onthe handle substrate.

In an example, the present invention provides a method for fabricating alaser diode device. The method includes providing a gallium and nitrogencontaining substrate member comprising a surface region, a releasematerial overlying the surface region, an n-type gallium and nitrogencontaining material; an active region overlying the n-type gallium andnitrogen containing material, a p-type gallium and nitrogen containingmaterial; and a first transparent conductive oxide region overlying thep-type gallium and nitrogen containing material, and an interface regionoverlying the conductive oxide material. The method includes bonding theinterface region to a handle substrate; and subjecting the releasematerial to an energy source to initiate release of the gallium andnitrogen containing substrate member. In an example, the method includesforming a ridge structure configured with the n-type gallium andnitrogen containing material, and forming a dielectric materialoverlying the n-type gallium and nitrogen containing material, andforming a second transparent conductive oxide material overlying anexposed portion of the n-type gallium and nitrogen containing materialsuch that active region is configured between the first transparentconductive oxide material and the second conductive oxide material tocause an optical guiding effect within the active region.

In an alternative example, the present invention provides a method forfabricating a laser diode device. The method includes providing agallium and nitrogen containing substrate member comprising a surfaceregion, a release material overlying the surface region, an n-typegallium and nitrogen containing material; an active region overlying then-type gallium and nitrogen containing material, a p-type gallium andnitrogen containing material; and a first transparent conductive oxideregion overlying the p-type gallium and nitrogen containing material,and an interface region overlying the conductive oxide material. Themethod includes bonding the interface region to a handle substrate; andsubjecting the release material to an energy source to initiate releaseof the gallium and nitrogen containing substrate member. The methodincludes forming an n-type contact region overlying an exposed portionof the n-type gallium and nitrogen containing material; forming apatterned second transparent oxide region overlying a portion of then-type contact region; and forming a thickness of metal materialoverlying the patterned transparent oxide region; wherein the p-typegallium and nitrogen containing material is configured as a ridgewaveguide structure to form a p-type ridge structure.

In an example, the present invention provides a method for fabricating alaser diode device. The method includes providing a gallium and nitrogencontaining substrate member comprising a surface region, a releasematerial overlying the surface region, an n-type gallium and nitrogencontaining material; an active region overlying the n-type gallium andnitrogen containing material, a p-type gallium and nitrogen containingmaterial; and a first transparent conductive oxide material overlyingthe p-type gallium and nitrogen containing material, and an interfaceregion overlying the conductive oxide material. The method includesbonding the interface region to a handle substrate and subjecting therelease material to an energy source to initiate release of the galliumand nitrogen containing substrate member. The method includes forming acavity member comprising a waveguide structure, a first end, and asecond end and forming the first end and second end by initiating acleaving process in the handle substrate material. In an example, alength of the cavity member is defined by the first cleaved end and thesecond cleaved end. The length of the cavity member is less than about1500 um, less than about 1000 um, less than about 600 um, less thanabout 400 um, or less than about 200 um.

In an example, the present invention provides a method for fabricating alaser diode device. The method includes providing a gallium and nitrogencontaining substrate member comprising a surface region, the surfaceregion characterized by a nonpolar or semipolar orientation; a releasematerial overlying the surface region, an n-type gallium and nitrogencontaining material; an active region overlying the n-type gallium andnitrogen containing material, a p-type gallium and nitrogen containingmaterial; and an interface region overlying the p-type gallium andnitrogen containing material. The method includes bonding the interfaceregion to a handle substrate; subjecting the release material to anenergy source to initiate release of the gallium and nitrogen containingsubstrate member and forming a cavity member comprising a waveguidestructure, a first end, and a second end. The method includes formingthe first end and second end by initiating a cleaving process in thehandle substrate material.

In an example, the present invention provides a method for fabricating alaser diode device. The method includes providing a gallium and nitrogencontaining substrate member comprising a surface region. The methodincludes forming a patterned dielectric material overlying the surfaceregion to expose a portion of the surface region within a vicinity of anrecessed region of the patterned dielectric material and maintaining anupper portion of the patterned dielectric material overlying coveredportions of the surface region. The method also includes performing alateral epitaxial growth overlying the exposed portion of the surfaceregion to fill the recessed region overlying the exposed portion andcausing a thickness of the lateral epitaxial growth to be formedoverlying the upper portion of the patterned dielectric material. Themethod includes forming an n-type gallium and nitrogen containingmaterial overlying the dielectric material, forming an active regionoverlying the n-type gallium and nitrogen containing material, forming ap-type gallium and nitrogen containing material, and forming a waveguidestructure in the p-type gallium and nitrogen containing material. Themethod also includes forming a transparent conductive oxide materialoverlying an exposed portion of the p-type gallium and nitrogencontaining material such that active region is configured between thetransparent dielectric material and the conductive oxide material tocause an optical guiding effect within the active region.

The present invention achieves these benefits and others in the contextof known process technology. However, a further understanding of thenature and advantages of the present invention may be realized byreference to the latter portions of the specification and attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a illustrates an epitaxial structure including sacrificial releaselayer, n-type gallium and nitrogen containing material, and activeregion and p-type gallium and nitrogen containing material is grown onbulk gallium and nitrogen containing substrate in an example.

FIG. 1b illustrates a transparent conductive oxide such as ITO isdeposited on the p-side (epi-surface) of the wafer in an example.Optionally, a metal contact layer could be deposited on the ITO.

FIG. 1c illustrates an ITO+epi-structure+GaN substrate is then bonded toa handle (carrier wafer) which could be InP, GaAs, silicon, or other.Indirect bonding or direct bonding could be used for this step in anexample.

FIG. 1d illustrates a GaN substrate is removed via one of severalpossible processes including PEC etching, laser ablation, CMP, etc. Forsome of these processes, a sacrificial layer may be necessary in anexample. After substrate removal, a thin GaN epi-membrane will be lefton top of the ITO and carrier wafer. Some p-side processing prior tobonding may be necessary depending on the final desired LD structure.The bonded epitaxially grown material will be thin<5 um. The laserstructure itself will be <1.5 um of that.

FIG. 2a is a simplified schematic of epi-structure grown on GaNsubstrate including a sacrificial layer in an example.

FIG. 2b is a simplified schematic of epi-structure grown on GaNsubstrate with a transparent conductive oxide such as ITO deposited ontop of the p-type gallium and nitrogen containing material and a carrierwafer bonded to the top of the stack in an example.

FIG. 2c is a simplified schematic of epi-structure with conductive oxideand carrier wafer after the gallium and nitrogen containing substratehas been removed in an example.

FIG. 2d is a simplified schematic of epi-structure with conductive oxideand carrier wafer after the gallium and nitrogen containing substratehas been removed in an example. The structure has been flipped over suchthat the carrier wafer is now the bottom of the stack.

FIG. 3a is an example schematic cross section of laser waveguide withdouble conductive oxide cladding showing ridge formation in n-typegallium and nitrogen containing material such as GaN in an example.

FIG. 3b is an example schematic cross section of laser waveguide withdouble conductive oxide cladding showing ridge formation in p-typegallium and nitrogen containing material such as GaN.

FIG. 3c is an example schematic cross section of laser waveguide withdouble conductive oxide cladding showing ridge formation in n-type andin p-type gallium and nitrogen containing material such as GaN.

FIG. 3d is an example schematic cross section of laser waveguide withconductive oxide and oxide or dielectric cladding showing ridgeformation in p-type gallium and nitrogen containing material such asGaN.

FIG. 4 is an example schematic of a conventional III-nitride laserstructure with AlGaN claddings.

FIG. 5 is an example 2D simulation for a double ITO cladding, singleside ridge blue laser structure. The GaN waveguiding/cladding layer ischanged from 800 nm on either side of the MQW active region to 100 nm oneither side of the MQW active region. By applying a thin cavity design,confinement factor in the active region can be improved significantly.

FIG. 6a shows schematic diagrams of direct versus indirect wafer bondingto the handle wafer. In the indirect bonding approach a layer such as ametal is used between the handle wafer and the gallium and nitrogencontaining epitaxial structure.

FIG. 6b is an example illustrating a preferred cleaved facet planealigned to the preferred cleavage plane of the handling wafer, scribingand cleaving the handling wafer will assist the cleaving of the GaNlaser facet. In this example m-plane GaN lasers wafer bonded to InP.Preferred cleaved facet plane must be aligned to the preferred cleavageplane of the handling wafer.

FIG. 7 is an example of a process flow that allows for direct bonding ofGaN epi to a carrier wafer and ITO.

FIG. 8a is an example of a process that allows for direct/indirectbonding of GaN epi to carrier wafer after the ridge has already beenformed.

FIG. 8b is an example of a process that allows for direct/indirectbonding of GaN epi to carrier wafer after the ridge has already beenformed using adhesion layer.

FIG. 9a is an example of SiO2 hard mask patterned and etched to exposeareas for growth initiation.

FIG. 9b is example of a first step n-GaN template growth.

FIG. 9c is an example of a second step n-GaN template growth wheregrowth conditions are altered such that sidewall growth is preferentialover planar growth. This is often called lateral epitaxial overgrowth(LEO).

FIG. 9d is an example of a LD structure including MQW active region,EBL, and pGaN are grown on top of the initiation and lateral overgrowthareas.

FIG. 9e is an example of an LEO process for forming a ridge waveguide.

FIG. 9f is an example of an LEO process for using deposited dielectric.

FIG. 9g is an example of an LEO process using deposited ITO and contact.

FIG. 9h is an example of an LEO process using an air-gap.

FIG. 10a is an example of patterning for defect reduction. In somesemipolar orientations, such as 20-21, 20-2-1, 11-22, 10-1-1, 10-11,etc., this method will help reduce basal plane MD densities underneaththe LD stripe by reducing the number of MDs allowed to form frompre-existing threading dislocations.

FIG. 10b is an example of patterning for defect reduction.

FIG. 10c is an example of Patterning for defect reduction. The substrateis patterned with SiO₂ in such a way that the stripes are oriented alongthe crystallographic direction which provides higher gain (i.e., inm-plane->c-direction, in 20-21->in-plane projection of the c-direction,etc.). Orientation of the stripes in this direction will be mosteffective in reducing the number of basal plane MDs since these MDs runperpendicular to the in-plane projected c-direction.

FIG. 11 is an example illustrating a ridge formed from TCO. Lateralindex contrast is provided by difference in index between n-side TCO andpassivating oxide. This is best where GaN cladding is thin or wheren-side GaN cladding is much thinner than p-side GaN cladding.

FIG. 12 is an example illustrating die expansion.

FIG. 13 is an example illustrating a ridge-less laser structure.

DESCRIPTION OF THE SPECIFIC EXAMPLES

The present disclosure relates generally to optical techniques. Morespecifically, the present disclosure provides methods and devices usingnonpolar, semi-polar, or polar c-plane oriented gallium and nitrogencontaining substrates for optical applications. In an example, thepresent disclosure describes the fabrication of a thin ultra-highconfinement factor ridge laser cavity composed of a low index upper andlower oxide cladding layers. Here, we describe multiple methods tofabricate this device:

-   -   1. Using lateral epitaxial overgrowth where a low index masking        material is used as the lower n-cladding material. TCO is        deposited on the p-side as the p-cladding material.    -   2. Using flip-chip substrate removal and ex-situ deposited TCO        as both the p- and n-cladding.

In an example, the present disclosure describes a method for fabricationan ridge LD cavity with an extremely high confinement factorimplementing ex-situ deposited oxide lower and upper cladding layers.The method described uses of lateral epitaxial overgrowth. In anexample, the device uses a patterned oxide mask deposited on a bare GaNsubstrate. In an example, the substrate may be a semipolar or nonpolargrowth orientation of GaN. In an example, the oxide patterned substrateis placed into a MOCVD and or MBE reactor for device growth. In anexample, the initial GaN template is grown in two steps: first step is agrowth initiation layer where planar growth parallel to the substratenormal is promoted; and second step is an overgrowth step where sidewallgrowth, parallel to the substrate surface is promoted. In an example,the sidewall growth rate is much faster than the planar growth rate.After sufficient sidewall growth, growth conditions are altered againfor planar growth of the LD structure. In an example, conventional ridgelaser process can be carried out on top of the winged region or on topof the unmasked window region. The transparent conductive oxide is usedas the top-side p-contact because of its low index. In an example,SiO2/(or air, if SiO2 is wet etched away) is used as a lower claddinglayer. In an example, LEO also provides a method for reducing MD densityand MD run length.

In an example, lateral epitaxial overgrowth (LEO) is a growth techniquefirst developed in the GaAs and Si community to reduce the density ofextended defects in the epitaxial structure. It was later employed inthe GaN community in order to reduce the high density of TDs and otherextended defects resulting from growth on foreign substrates such assapphire and SiC. The technique involves masking regions of thesubstrate with a material that does not allow epitaxial growth of GaN.Common materials are SiO2, TiN, SiN, etc. Epitaxial growth will occur inthe unmasked regions. When the epitaxial growth in the unmasked regionsurfaces above the masked region, sidewall growth will occur. If thegrowth conditions are optimized, sidewall growth may be preferentialover planar growth. This results in “window” regions and “wing” regions.Window regions refer to the original unmasked area, where defects fromthe substrate and/or substrate/epi-layer interface can extend into theepitaxial structure. Wing regions, refer to the overgrowth area wheredefects can be reduced several orders of magnitude in comparison to the“window” regions.

This patent describes a method to incorporate LEO growth on bulknonpolar/semipolar substrates to fabricate an ultra-high confinementfactor ridge laser cavity. The laser may be fabricated via differentprocessing steps. FIG. 1(a)-1(h) describes two of the variations.

The process starts with a bare substrate on which SiO2 (or any othermasking material that does not allow GaN growth) is patterned usingconventional photolithography and/or dry/wet etching steps. Postpatterning, the substrate is loaded into the epitaxial growth reactor.The growth begins with a nucleation layer inside the “window” region.After the nucleation layer achieves planar growth and surfaces above themasking material, the growth conditions in the reactor are altered suchthat sidewall growth is preferential over planar growth. Changes to thegrowth condition may include temperature, V/III ratios, total gas flow,different precursors, and doping. The sidewall growth may extend forseveral microns until a relatively large wing region is produced. Thegrowth conditions are then changed again to grow the planar epitaxiallaser structure.

After the epitaxial growth, convention laser ridge processing is carriedout either on top of the “wing” region (variation 1) or on top of the“window” region (variation 2). In the case of variation 1, the low indexmasking material underneath the wing region acts as the lower claddingmaterial. In variation 2, the partial exposure of the mode to the lowerindex masking material helps with lateral confinement. TCO (transparentconductive oxide)/metal contact is deposited on top of the ridge afterridge processing to form a contact as well as a low index upper claddinglayer.

Another variation of this process includes wet etching away the maskingmaterial resulting in a low index air gap as the lower cladding layer asseen in FIG. 1(h).

The use of TCO as an upper cladding layer has been demonstrated byresearchers at UCSB and PARC. This patent, however, includes the use ofa low index masking material as the lower cladding layer. The result isa very thin, high confinement factor laser ridge cavity.

Another advantage of this LEO method for fabrication an ultra-highconfinement factor ridge laser cavity is the reduction in threadingdislocation (TD) density after LEO wing growth. There is an overallreduction in TD density because the wing region should be effectivelyfree of TDs. This results in fewer number of TDs that can bend and glidealong highly strained heterointerface in the epi-structure. We believethis will be an effective method for reducing MD density and increasingthe critical thickness in semipolar heteroepitaxy. This idea isschematically shown in FIGS. 2(a) and 2(b).

The most effective way of using LEO to reduce density of bending andgliding TDs while maximizing the area of useable substrate is to patternthe wafer with masking material along the in-plane projection of [0001].This is because MD formation in semipolar heteroepitaxial growth occursmost readily by dislocation arrays oriented orthogonal to the in-planeprojection of [0001]. Moreover, this allows fabrication of ridge lasercavities with stripes oriented along the in-plane projection of [0001]which has higher optical gain than ridge laser stripes orientedorthogonal to the in-plane projection of [0001]. This is shown in FIG.3.

This high confinement of the structure may also help reduce asymmetricoptical substrate anomalies with the lower masking oxide/claddingmaterial acting as an optical blocking layer.

In an example, this method uses conventional planar growth of a LDepi-structure on either nonpolar/semipolar/polar GaN substrates. Atransparent conductive oxide (TCO) is then deposited on the freeepitaxial surface to form a transparent, conductive contact layer withan index of refraction lower than GaN or AlGaN films of compositionsthat can be grown fully strained at the thicknesses needed to providesufficient confinement of the optical mode. Two example TCOs are indiumtin oxide (ITO) and zinc oxide (ZnO). ITO is the commercial standard forTCOs, and is used in a variety of fields including displays and solarcells where a semi-transparent electrical contact is desired. ZnO offersthe advantage of being a direct gap semiconductor with the same crystalstructure as GaN and can be grown epitaxially on GaN at temperaturesrelatively low compared to growth temperatures of AlInGaN alloys. Thebandgap of ZnO is also sufficiently large and similar to GaN (approx.3.3 eV) that it will exhibit negligible band-edge absorption of visiblewavelengths of light. ZnO can be deposited in a variety of ways such asmetal organic chemical vapor deposition, other vapor depositiontechniques, and from a solution.

The wafer is then bonded to a handle, with the free-surface of the TCOadjacent to the bonding interface. The bonding can either be direct,i.e. with the TCO in contact with the handle material, or indirect, i.e.with a bonding media disposed between the TCO and the handle material inorder to improve the bonding characteristics. For example, this bondingmedia could be Au—Sn solder, CVD deposited SiO2, a polymer, CVD orchemically deposited polycrystalline semiconductor or metal, etc.Indirect bonding mechanisms may include thermocompression bonding,anodic bonding, glass frit bonding, bonding with an adhesive with thechoice of bonding mechanism dependent on the nature of the bondingmedia.

Thermocompression bonding involves bonding of wafers at elevatedtemperatures and pressures using a bonding media disposed between theTCO and handle wafer. The bonding media may be comprised of a number ofdifferent layers, but typically contain at least one layer (the bondinglayer) that is composed of a relatively ductile material with a highsurface diffusion rate. In many cases this material is either Au, Al orCu. The bonding stack may also include layers disposed between thebonding layer and the TCO or handle wafer that promote adhesion or actas diffusion barriers should the species in the TCO or handle wafer havea high solubility in the bonding layer material. For example an Aubonding layer on a Si wafer may result in diffusion of Si to the bondinginterface, which would reduce the bonding strength. Inclusion of adiffusion barrier such as silicon oxide or nitride would limit thiseffect. Relatively thin layers of a second material may be applied onthe top surface of the bonding layer in order to promote adhesionbetween the bonding layers disposed on the TCO and handle. Some bondinglayer materials of lower ductility than gold (e.g. Al, Cu etc.) or whichare deposited in a way that results in a rough film (for exampleelectrolytic deposition) may require planarization or reduction inroughness via chemical or mechanical polishing before bonding, andreactive metals may require special cleaning steps to remove oxides ororganic materials that may interfere with bonding.

Metal layer stacks may be spatially non-uniform. For example, theinitial layer of a bonding stack may be varied using lithography toprovide alignment or fiducial marks that are visible from the backsideof the transparent substrate.

Thermocompressive bonding can be achieved at relatively lowtemperatures, typically below 500 degrees Celsius and above 200.Temperatures should be high enough to promote diffusivity between thebonding layers at the bonding interface, but not so high as to promoteunintentional alloying of individual layers in each metal stack.Application of pressure enhances the bond rate, and leads to someelastic and plastic deformation of the metal stacks that brings theminto better and more uniform contact. Optimal bond temperature, time andpressure will depend on the particular bond material, the roughness ofthe surfaces forming the bonding interface and the susceptibility tofracture of the handle wafer or damage to the device layers under load.

The bonding interface need not be composed of the totality of the wafersurface. For example, rather than a blanket deposition of bonding metal,a lithographic process could be used to deposit metal in discontinuousareas separated by regions with no bonding metal. This may beadvantageous in instances where defined regions of weak or no bondingaid later processing steps, or where an air gap is needed. One exampleof this would be in removal of the GaN substrate using wet etching of anepitaxially grown sacrificial layer. To access the sacrificial layer onemust etch vias into either of the two surfaces of the epitaxial wafer,and preserving the wafer for re-use is most easily done if the vias areetched from the bonded side of the wafer. Once bonded, the etched viasresult in channels that can conduct etching solution from the edges tothe center of the bonded wafers, and therefore the areas of thesubstrate comprising the vias are not in intimate contact with thehandle wafer such that a bond would form.

The bonding media can also be an amorphous or glassy material bondedeither in a reflow process or anodically. In anodic bonding the media isa glass with high ion content where mass transport of material isfacilitated by the application of a large electric field. In reflowbonding the glass has a low melting point, and will form contact and agood bond under moderate pressures and temperatures. All glass bonds arerelatively brittle, and require the coefficient of thermal expansion ofthe glass to be sufficiently close to the bonding partner wafers (i.e.the GaN wafer and the handle). Glasses in both cases could be depositedvia vapor deposition or with a process involving spin on glass. In bothcases the bonding areas could be limited in extent and with geometrydefined by lithography or silk-screening process.

Direct bonding between TCO deposited on both the GaN and handle wafers,of the TCO to the handle wafer or between the epitaxial GaN film and TCOdeposited on the handle wafer would also be made at elevatedtemperatures and pressures. Here the bond is made by mass transport ofthe TCO, GaN and/or handle wafer species across the bonding interface.Due to the low ductility of TCOs the bonding surfaces must besignificantly smoother than those needed in thermocompressive bonding ofmetals like gold.

The embodiments of this invention will typically include a ridge of somekind to provide lateral index contrast that can confine the optical modelaterally. One embodiment would have the ridge etched into theepitaxially grown GaN cladding layers. In this case, it does not matterwhether the ridge is etched into the p-type GaN layer before TCOdeposition and bonding or into the n-type layer after bonding andremoval of the substrate. In the former case, the TCO would have to beplanarized somehow to provide a surface conducive to bonding unless areflowable or plastically deformable bonding media is used which couldaccommodate large variations in height on the wafer surface. In thelatter case bonding could potentially be done without further modifyingthe TCO layer. Planarization may be required in either case should theTCO deposition technique result in a sufficiently rough TCO layer as tohinder bonding to the handle wafer.

In the case where a ridge is formed either partially or completely withthe TCO, the patterned wafer could be bonded to the handle, leaving airgaps on either side of the ridge, thereby maximizing the index contrastbetween the ridge and surrounding materials.

After p-side ridge processing, ITO is deposited as the p-contact.Following ITO deposition, the wafer is bonded p-side down to a carrierwafer and the bulk of the substrate is removed via laser lift-off orphotochemical etching (PEC). This will require some kind of sacrificiallayer on the n-side of the epi-structure.

Laser ablation is a process where an above-band-gap emitting laser isused to decompose an absorbing sacrificial (Al,In,Ga)N layer by heatingand inducing desorption of nitrogen. The remaining Ga sludge is thenetched away using aqua regia or HCl. This technique can be usedsimilarly to PEC etching in which a sacrificial material between theepitaxial device and the bulk substrate is etched/ablated away resultingin separation of the epitaxial structure and the substrate. Theepitaxial film (already bonded to a handling wafer) can then be lappedand polished to achieve a planar surface.

PEC etching is a photoassisted wet etch technique that can be used toetch GaN and its alloys. The process involves an above-band-gapexcitation source and an electrochemical cell formed by thesemiconductor and the electrolyte solution. In this case, the exposed(Al,In,Ga)N material surface acts as the anode, while a metal paddeposited on the semiconductor acts as the cathode. The above-band-gaplight source generates electron-hole pairs in the semiconductor.Electrons are extracted from the semiconductor via the cathode whileholes diffuse to the surface of material to form an oxide. Since thediffusion of holes to the surface requires the band bending at thesurface to favor a collection of holes, PEC etching typically works onlyfor n-type material although some methods have been developed foretching p-type material. The oxide is then dissolved by the electrolyteresulting in wet etching of the semiconductor. Different types ofelectrolyte including HCl, KOH, and HNO₃ have been shown to be effectivein PEC etching of GaN and its alloys. The etch selectivity and etch ratecan be optimized by selecting a favorable electrolyte. It is alsopossible to generate an external bias between the semiconductor and thecathode to assist with the PEC etching process.

After laser lift-off, ITO is deposited as the n-contact. One version ofthis process flow using laser lift-off is described in FIGS. 4(a) and4(b). Using this method, the substrate can be subsequently polished andreused for epitaxial growth. Sacrificial layers for laser lift-off areones that can be included in the epitaxial structure between the lightemitting layers and the substrate. These layers would have theproperties of not inducing significant amounts of defects in the lightemitting layers while having high optical absorption at the wavelengthsused in the laser lift-off process. Some possible sacrificial layersinclude epitaxially grown layers that are fully strained to thesubstrate which are absorbing either due to bandgap, doping or pointdefectivity due to growth conditions, ion implanted layers where theimplantation depth is well controlled and the implanted species andenergy are tuned to maximize implantation damage at the sacrificiallayer and patterned layers of foreign material which will act as masksfor lateral epitaxial overgrowth.

Sacrificial layers for lift-off of the substrate via photochemicaletching would incorporate at a minimum a low-bandgap or doped layer thatwould absorb the pump light and have enhanced etch rate relative to thesurrounding material. The sacrificial layer can be deposited epitaxiallyand their alloy composition and doping of these can be selected suchthat hole carrier lifetime and diffusion lengths are high. Defects thatreduce hole carrier lifetimes and diffusion length must can be avoidedby growing the sacrificial layers under growth conditions that promotehigh material crystalline quality. An example of a sacrificial layerwould be InGaN layers that absorb at the wavelength of an external lightsource. An etch stop layer designed with very low etch rate to controlthe thickness of the cladding material remaining after substrate removalcan also be incorporated to allow better control of the etch process.The etch properties of the etch stop layer can be controlled solely byor a combination of alloy composition and doping. A potential etch stoplayer would an AlGaN layer with a bandgap higher than the external lightsource. Another potential etch stop layer is a highly doped n-type AlGaNor GaN layer with reduce minority carrier diffusion lengths and lifetimethereby dramatically reducing the etch rate of the etch stop material.

PEC etching can be done before or after direct/indirect bonding of thefree surface of the TCO to the handle material. In one case, the PECetching is done after bonding of the p-side TCO to the handle materialand the PEC etch releases the III-nitride epitaxial material from theGaN substrate. In another case, PEC etching of the sacrificial layer isdone before bonding such that most of the sacrificial layer is removedand the III-nitride epitaxial material is held mechanically stable onthe GaN substrate via small unetched regions. Such regions can be leftunetched due to significant decrease in etch rates around dislocationsor defects. TCO is then deposited on the epitaxial material and the TCOfree surface is bonded to a handle wafer that can be composed of variousmaterials. After bonding, mechanical force is applied to the handlewafer and GaN substrate to complete the release of III-nitride epitaxialmaterial from the GaN substrate.

Substrate removal can also be achieved by mechanical lapping andpolishing or chemical-mechanical lapping and polishing, in which casethe substrate cannot be recovered. In cases where the laterallyconfining structure is on the bonded p-side of the wafer the substrateneed only be thinned enough to facilitate good cleaving, in which caselapping and polishing may be an ideal removal technique.

Both the LEO and substrate removal method can result in very thin LDcavities with very high confinement factors. As an example, FIG. 5(a)and FIG. 5(b) show the optical mode confinement of a standard blue LDstructure and one with ITO cladding layers, respectively. Thewaveguiding structures of the two LDs are different, but the activeregions are identical. By using ITO cladding, the confinement factor isincreased from 12.04% to 17.56%.

In addition to providing ultra high confinement active regions, thiswafer bonding technique for the fabrication of Ga-based laser diodes canalso lead to improved cleaved facet quality. Specifically, we describe amethod for fabricating cleaved facets along a vertical plane for NP andSP ridge laser structures grown on bulk GaN substrates.

Achieving a high quality cleaved facet for NP and SP ridge lasers can beextremely difficult due to the nature of the atomic bonding on thecrystallographic planes that are orthogonal to a laser stripe orientedin the c-direction or the projection of the c-direction. In nonpolarm-plane, the desired ridge orientation is along the c-direction.Therefore, facets must be form on a crystallographic plane orthogonal tothe c-direction (the c-plane). While this can be done in practice, theyield tends to be low and the facet qualities often vary. This is inpart due to the high iconicity and bond strength on the c-plane, whichmake cleaving difficult. In some SP orientations, it is possible toachieve vertical cleavage planes that are orthogonal to the ridgedirection—however, yields also tend to be low. In other SP orientations,vertical cleavage planes orthogonal to the ridge direction simply do notexist. Cleaving in these SP orientations often result in facets that'sare grossly angled.

In this wafer bonding process invention the epitaxial laser structuregrown on top of the gallium and nitrogen containing substrate is bondedp-side down on top of a handling wafer. This can be done before/aftertop-side processing depending on the desired resulting LD structure. Thehandling wafer material and crystal orientation is selected to haveeasily achievable vertical cleavage planes (examples of such materialsinclude Si, GaAs, InP, etc.). The LD wafer and the handling wafer can becrystallographically aligned such that the preferable cleavage directionof the handling wafer coincides with the desired cleavage plane of theridge LD structure. The LD wafer and the handling wafer are thendirectly or indirectly bonded together. After bonding, the bulk GaNsubstrate can be removed via PEC etching, laser ablation, or CMP.

Since the resulting LD epitaxial film will be thin (<5 um), scribe marksshould be penetrate the epi-film completely and into the bonding wafer.Forcing a clean cleave across the desired crystallographic plane shouldnow be easy since there is limited amount of actual epi-material tobreak. This method may also allow fabrication of cleaved facet LDs oncertain SP orientations that was previously not possible.

The handling wafer can be selected from several possibilities including,but not limited to 6H—SiC, Si, sapphire, MgAl₂O₄ spinel, MgO, ZnO,ScAlMgO₄, GaAsInP, TiO₂, Quartz, LiAlO2.

The above described method can also be extended into the process for dieexpansion. Typical dimensions for laser cavity widths are 1-30 μm, whilewire bonding pads are ˜100 μm wide. This means that if the wire bondingpad width restriction and mechanical handling considerations wereeliminated from the GaN chip dimension between >3 and 100 times morelaser diode die could be fabricated from a single epitaxial gallium andnitrogen containing wafer. This translates to a >3 to 100 timesreduction in epitaxy and substrate costs. In certain device designs, therelatively large bonding pads are mechanically supported by the epitaxywafer, although they make no use of the material properties of thesemiconductor beyond structural support. The current invention allows amethod for maximizing the number of GaN laser devices which can befabricated from a given epitaxial area on a gallium and nitrogencontaining substrate by spreading out the epitaxial material on acarrier wafer such that the wire bonding pads or other structuralelements are mechanically supported by relatively inexpensive carrierwafer, while the light emitting regions remain fabricated from thenecessary epitaxial material.

In an embodiment, mesas of gallium and nitrogen containing laser diodeepitaxy material are fabricated in a dense array on a gallium andnitrogen containing substrate. This pattern pitch will be referred to asthe ‘first pitch’. Each of these mesas is a ‘die’. These die are thentransferred to a carrier wafer at a second pitch where the second pitchis greater than the first pitch. The second die pitch allows for easymechanical handling and room for wire bonding pads positioned in theregions of carrier wafer in-between epitaxy mesas, enabling a greaternumber of laser diodes to be fabricated from a given gallium andnitrogen containing substrate and overlying epitaxy material. This isreferred to as “die expansion,” or other terms consistent with ordinarymeaning for one of ordinary skill in the art.

FIG. 11—Side view illustrations of gallium and nitrogen containingepitaxial wafer 100 before the die expansion process and carrier wafer1206 after the die expansion process. This figure demonstrates a roughlyfive times expansion and thus five times improvement in the number oflaser diodes which can be fabricated from a single gallium and nitrogencontaining substrate and overlying epitaxial material. Typical epitaxialand processing layers are included for example purposes and are n-GaNand n-side cladding layers 1201, active region 1202, p-GaN and p-sidecladding 1203, insulating layers 1204, and contact/pad layers 105.Additionally, a sacrificial region 1207 and bonding material 1208 areused during the die expansion process.

In another embodiment, die expansion can be used to fabricate“ridge-less” lasers in which the epitaxial material of the entire oralmost entire mesa stripe is utilized in the laser. This differs fromthe traditional ridge laser structure where a ridge is etched into theepitaxial material to form an index guided laser. In this embodiment fora ridge-less laser, the entire mesa is used as a gain guided laserstructure. First mesas are etched and transferred onto a carrier wafervia direct/indirect bonding. The gallium and nitrogen containingsubstrate is removed, leaving the etched mesas on the carrier wafer at adie pitch larger than the original die pitch on the gallium and nitrogencontaining carrier wafer. Dielectric material is deposited on thesidewalls of the mesa to insulate the p- and n-contacts. The dielectricmaterial does not cover the entirety of the gallium and nitrogencontaining p-contact surface. Metal or TCO is deposited on the galliumand nitrogen containing p-contact surface to form the p-contacts. Thisis an exemplary process in which a ridge-less LD structure may be formthrough the invention described in this patent.

FIG. 13 cross-section schematic of a ridge-less laser structurefabricated using the current invention. The epitaxial material 1306 istransferred onto a carrier wafer 1301 using the techniques discussed inthe current invention. Bonding of the epitaxial material 1306 to thecarrier wafer 1301 can be done so via indirect metal 1302 to metal 1302thermo-compressive bonding. The epitaxial material is cladded on the p-and n-side using TCO 1304 to provide high modal confinement in the MQWactive region 1307. Insulating material 1303 is deposited on thesidewalls of the mesa to insulate the p- and n-contacts. Top-side metalpad contact 1305 is formed on top of the top side TCO 1304.

In an example, the present techniques provide for a method forfabricating a laser diode device. The method includes providing agallium and nitrogen containing substrate member comprising a surfaceregion, a release material overlying the surface region, an n-typegallium and nitrogen containing material; an active region overlying then-type gallium and nitrogen containing material, a p-type gallium andnitrogen containing material; and an interface region overlying thep-type gallium and nitrogen containing material. The method includesbonding the interface region to a handle substrate; and subjecting therelease material to an energy source, using at least PEC etching, toinitiate release of the gallium and nitrogen containing substratemember, while maintaining attachment of the handle substrate via theinterface region. The method also includes forming a contact region toeither or both the n-type gallium and nitrogen containing material orthe p-type gallium and nitrogen containing material.

Referring now back to FIG. 6a —The epitaxial LD structure and the GaNsubstrate may be bonded directly or indirectly to a handling wafer.Direct wafer bonding is bonding without the application of intermediatelayers (i.e., GaN directly onto GaAs). Indirect wafer bonding is bondingwith the application of an intermediate adhesion layer. When theadhesion layer material is comprised of a metal alloy, the process isoften referred to as eutectic bonding.

FIG. 6b —For the cleave to translate from the bonding wafer into thethin GaN LD membrane, the two wafers must be crystallographicallyaligned before bonding. Here, the GaN (0001) plane (or the [11-20]direction) for an m-plane LD is aligned with InP (011) plane (or [0-11]direction).

FIG. 7—Wafer bonding is sensitive to surface roughness and topography.Smooth surfaces are typically required for high yield direct waferbonding. Direct wafer bonding of a handling wafer onto the ridge side ofthe LD structure would therefore likely require a pre-etched handlingwafer. The pre-etched handling wafer would allow the wafer bonding tooccur only on the exposed GaN ridge and not on the contact pads. This isdepicted in the cross-sectional schematic in FIG. 3a . The use of apre-etched handling wafer would also be applicable in the case whereindirect bonding is used (FIG. 3b ). Note, this pre-etched handlingwafer is only necessary if there is exists a rough surface topographythat may degrade the wafer bonding yield. A non-etched handling wafermay be used if bonding between two planar wafers is desired.

In an example, the present invention can be applied to a variety ofapplications, such as mobile displays, micro displays, and otherdevices. An example of a mobile device is known as Google Glass, whichhas been described in part below, See also www.wikipedia.com.

-   -   “Camera    -   Google Glass has the ability to take photos and record 720p HD        video. While video is recording, the screen stays on.    -   Touchpad    -   A man controls Google Glass using the touchpad built into the        side of the device    -   A touchpad is located on the side of Google Glass, allowing        users to control the device by swiping through a timeline-like        interface displayed on the screen. Sliding backward shows        current events, such as weather, and sliding forward shows past        events, such as phone calls, photos, circle updates, etc.    -   Technical specifications    -   For the developer Explorer units:    -   Android 4.0.4 and higher    -   640×360 display    -   5-megapixel camera, capable of 720p video recording    -   Wi-Fi 802.11b/g    -   Bluetooth    -   16 GB storage (12 GB available)    -   Texas Instruments OMAP 4430 SoC 1.2 Ghz Dual (ARMv7)    -   682 MB RAM “proc”.    -   3 axis gyroscope    -   3 axis accelerometer    -   3 axis magnetometer (compass)    -   Ambient light sensing and proximity sensor    -   Bone conduction transducer.”

In an example, the present laser device and module can be configured ona display of a smart phone, which includes the following features (whichare found in an iPhone 4 from Apple Computer, although there can bevariations), see www.apple.com.

-   -   “GSM model: UMTS/HSDPA/HSUPA (850, 900, 1900, 2100 MHz);        GSM/EDGE (850, 900, 1800, 1900 MHz)    -   CDMA model: CDMA EV-DO Rev. A (800, 1900 MHz)    -   802.11b/g/n Wi-Fi (802.11n 2.4 GHz only)    -   Bluetooth 2.1+EDR wireless technology    -   Assisted GPS    -   Digital compass    -   Wi-Fi    -   Cellular    -   Retina display    -   3.5-inch (diagonal) widescreen Multi-Touch display    -   800:1 contrast ratio (typical)    -   500 cd/m2 max brightness (typical)    -   Fingerprint-resistant oleophobic coating on front and back    -   Support for display of multiple languages and characters        simultaneously    -   5-megapixel iSight camera    -   Video recording, HD (720p) up to 30 frames per second with audio    -   VGA-quality photos and video at up to 30 frames per second with        the front camera    -   Tap to focus video or still images    -   LED flash    -   Photo and video geotagging    -   Built-in rechargeable lithium-ion battery    -   Charging via USB to computer system or power adapter    -   Talk time: Up to 7 hours on 3G, up to 14 hours on 2G (GSM)    -   Standby time: Up to 300 hours    -   Internet use: Up to 6 hours on 3G, up to 10 hours on Wi-Fi    -   Video playback: Up to 10 hours    -   Audio playback: Up to 40 hours    -   Frequency response: 20 Hz to 20,000 Hz    -   Audio formats supported: AAC (8 to 320 Kbps), Protected AAC        (from iTunes Store), HE-AAC, MP3 (8 to 320 Kbps), MP3 VBR,        Audible (formats 2, 3, 4, Audible Enhanced Audio, AAX, and        AAX+), Apple Lossless, AIFF, and WAV    -   User-configurable maximum volume limit    -   Video out support at up to 720p with Apple Digital AV Adapter or        Apple VGA Adapter; 576p and 480p with Apple Component AV Cable;        576i and 480i with Apple Composite AV Cable (cables sold        separately)    -   Video formats supported: H.264 video up to 720p, 30 frames per        second, Main Profile Level 3.1 with AAC-LC audio up to 160 Kbps,        48 kHz, stereo audio in .m4v, .mp4, and .mov file formats;        MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per        second, Simple Profile with AAC-LC audio up to 160 Kbps per        channel, 48 kHz, stereo audio in .m4v, .mp4, and .mov file        formats; Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels,        30 frames per second, audio in ulaw, PCM stereo audio in .avi        file format    -   Three-axis gyro    -   Accelerometer    -   Proximity sensor    -   Ambient light sensor.”

An exemplary electronic device may be a portable electronic device, suchas a media player, a cellular phone, a personal data organizer, or thelike. Indeed, in such embodiments, a portable electronic device mayinclude a combination of the functionalities of such devices. Inaddition, the electronic device may allow a user to connect to andcommunicate through the Internet or through other networks, such aslocal or wide area networks. For example, the portable electronic devicemay allow a user to access the internet and to communicate using e-mail,text messaging, instant messaging, or using other forms of electroniccommunication. By way of example, the electronic device may be a modelof an iPod having a display screen or an iPhone available from AppleInc.

In certain embodiments, the device may be powered by one or morerechargeable and/or replaceable batteries. Such embodiments may behighly portable, allowing a user to carry the electronic device whiletraveling, working, exercising, and so forth. In this manner, anddepending on the functionalities provided by the electronic device, auser may listen to music, play games or video, record video or takepictures, place and receive telephone calls, communicate with others,control other devices (e.g., via remote control and/or Bluetoothfunctionality), and so forth while moving freely with the device. Inaddition, device may be sized such that it fits relatively easily into apocket or a hand of the user. While certain embodiments of the presentinvention are described with respect to a portable electronic device, itshould be noted that the presently disclosed techniques may beapplicable to a wide array of other, less portable, electronic devicesand systems that are configured to render graphical data, such as adesktop computer.

In the presently illustrated embodiment, the exemplary device includesan enclosure or housing, a display, user input structures, andinput/output connectors. The enclosure may be formed from plastic,metal, composite materials, or other suitable materials, or anycombination thereof. The enclosure may protect the interior componentsof the electronic device from physical damage, and may also shield theinterior components from electromagnetic interference (EMI).

The display may be a liquid crystal display (LCD), a light emittingdiode (LED) based display, an organic light emitting diode (OLED) baseddisplay, or some other suitable display. In accordance with certainembodiments of the present invention, the display may display a userinterface and various other images, such as logos, avatars, photos,album art, and the like. Additionally, in one embodiment, the displaymay include a touch screen through which a user may interact with theuser interface. The display may also include various function and/orsystem indicators to provide feedback to a user, such as power status,call status, memory status, or the like. These indicators may beincorporated into the user interface displayed on the display.

In an example, the device also includes a laser module configured with amicrodisplay to form a light engine. Examples of the RGB module havebeen described throughout the present specification. Micro-displays canbe comprised of a scanning MEMS mirror, an LCOS chip, or a digital lightprocessing chip.

According to an embodiment, the present invention provides a projectionsystem. The projection system includes an interface for receiving video.The system also includes an image processor for processing the video.The system includes a light source including a plurality of laserdiodes. The plurality of laser diodes includes a blue laser diode. Theblue laser diode is fabricated on non-polar oriented gallium nitridematerial. The system includes a power source electrically coupled to thelight source.

According to another embodiment, the present invention provides aprojection system. The system includes an interface for receiving video.The system also includes an image processor for processing the video.The system includes a light source including a plurality of laserdiodes. The plurality of laser diodes includes a blue laser diode. Theblue laser diode is fabricated on semi-polar oriented gallium nitridematerial. The system also includes a power source electrically coupledto the light source.

According to an embodiment, the present invention provides a projectionapparatus. The projection apparatus includes a housing having anaperture. The apparatus also includes an input interface for receivingone or more frames of images. The apparatus includes a video processingmodule. Additionally, the apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The laser source is configured produce a laser beam bycombining outputs from the blue, green, and red laser diodes. Theapparatus also includes a laser driver module coupled to the lasersource. The laser driver module generates three drive currents based ona pixel from the one or more frames of images. Each of the three drivecurrents is adapted to drive a laser diode. The apparatus also includesa microelectromechanical system (MEMS) scanning mirror, or “flyingmirror”, configured to project the laser beam to a specific locationthrough the aperture resulting in a single picture. By rastering thepixel in two dimensions a complete image is formed. The apparatusincludes an optical member provided within proximity of the lasersource, the optical member being adapted to direct the laser beam to theMEMS scanning mirror. The apparatus includes a power source electricallycoupled to the laser source and the MEMS scanning mirror.

According to an embodiment, the present invention provides a projectionapparatus. The projection apparatus includes a housing having anaperture. The apparatus also includes an input interface for receivingone or more frames of images. The apparatus includes a video processingmodule. Additionally, the apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. In this embodiment, the blue andthe green laser diode would share the same substrate. The red lasercould be fabricated from AlInGaP. The laser source is configured producea laser beam by combining outputs from the blue, green, and red laserdiodes. The apparatus also includes a laser driver module coupled to thelaser source. The laser driver module generates three drive currentsbased on a pixel from the one or more frames of images. Each of thethree drive currents is adapted to drive a laser diode. The apparatusalso includes a MEMS scanning mirror, or “flying mirror”, configured toproject the laser beam to a specific location through the apertureresulting in a single picture. By rastering the pixel in two dimensionsa complete image is formed. The apparatus includes an optical memberprovided within proximity of the laser source, the optical member beingadapted to direct the laser beam to the MEMS scanning mirror. Theapparatus includes a power source electrically coupled to the lasersource and the MEMS scanning mirror.

According to an embodiment, the present invention provides a projectionapparatus. The projection apparatus includes a housing having anaperture. The apparatus also includes an input interface for receivingone or more frames of images. The apparatus includes a video processingmodule. Additionally, the apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. In this embodiment, two or more of the different colorlasers would be packaged together in the same enclosure. In thiscopackaging embodiment, the outputs from the blue, green, and red laserdiodes would be combined into a single beam. The apparatus also includesa laser driver module coupled to the laser source. The laser drivermodule generates three drive currents based on a pixel from the one ormore frames of images. Each of the three drive currents is adapted todrive a laser diode. The apparatus also includes amicroelectromechanical system (MEMS) scanning mirror, or “flyingmirror”, configured to project the laser beam to a specific locationthrough the aperture resulting in a single picture. By rastering thepixel in two dimensions a complete image is formed. The apparatusincludes an optical member provided within proximity of the lasersource, the optical member being adapted to direct the laser beam to theMEMS scanning mirror. The apparatus includes a power source electricallycoupled to the laser source and the MEMS scanning mirror.

According to another embodiment, the present invention provides aprojection apparatus. The apparatus includes a housing having anaperture. The apparatus includes an input interface for receiving one ormore frames of images. The apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The laser source is configured produce a laser beam bycombining outputs from the blue, green, and red laser diodes. Theapparatus includes a digital light processing (DLP) chip comprising adigital mirror device. The digital mirror device including a pluralityof mirrors, each of the mirrors corresponding to one or more pixels ofthe one or more frames of images. The apparatus includes a power sourceelectrically coupled to the laser source and the digital lightprocessing chip. Many variations of this embodiment could exist, such asan embodiment where the green and blue laser diode share the samesubstrate or two or more of the different color lasers could be housedin the same packaged. In this copackaging embodiment, the outputs fromthe blue, green, and red laser diodes would be combined into a singlebeam.

According to another embodiment, the present invention provides aprojection apparatus. The apparatus includes a housing having anaperture. The apparatus includes an input interface for receiving one ormore frames of images. The apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The apparatus includes a digital light processing chip(DLP) comprising three digital mirror devices. Each of the digitalmirror devices includes a plurality of mirrors. Each of the mirrorscorresponds to one or more pixels of the one or more frames of images.The color beams are respectively projected onto the digital mirrordevices. The apparatus includes a power source electrically coupled tothe laser sources and the digital light processing chip. Many variationsof this embodiment could exist, such as an embodiment where the greenand blue laser diode share the same substrate or two or more of thedifferent color lasers could be housed in the same packaged. In thiscopackaging embodiment, the outputs from the blue, green, and red laserdiodes would be combined into a single beam.

As an example, the color wheel may include phosphor material thatmodifies the color of light emitted from the light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes blue and red light sources. The color wheel includes aslot for the blue color light and a phosphor containing region forconverting blue light to green light. In operation, the blue lightsource (e.g., blue laser diode or blue LED) provides blue light throughthe slot and excites green light from the phosphor containing region;the red light source provides red light separately. The green light fromthe phosphor may be transmitted through the color wheel, or reflectedback from it. In either case the green light is collected by optics andredirected to the microdisplay. The blue light passed through the slotis also directed to the microdisplay. The blue light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.Alternatively, a green laser diode may be used, instead of a blue laserdiode with phosphor, to emit green light. It is to be appreciated thatcan be other combinations of colored light sources and color wheelsthereof.

As another example, the color wheel may include multiple phosphormaterials. For example, the color wheel may include both green and redphosphors in combination with a blue light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a blue light source. The color wheel includes a slot forthe blue laser light and two phosphor containing regions for convertingblue light to green light, and blue light and to red light,respectively. In operation, the blue light source (e.g., blue laserdiode or blue LED) provides blue light through the slot and excitesgreen light and red light from the phosphor containing regions. Thegreen and red light from the phosphor may be transmitted through thecolor wheel, or reflected back from it. In either case the green and redlight is collected by optics and redirected to the microdisplay. Theblue light source may be a laser diode or LED fabricated on non-polar orsemi-polar oriented GaN. It is to be appreciated that can be othercombinations of colored light sources and color wheels thereof.

As another example, the color wheel may include blue, green, and redphosphor materials. For example, the color wheel may include blue, greenand red phosphors in combination with a ultra-violet (UV) light source.In a specific embodiment, color wheel includes multiple regions, each ofthe regions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a UV light source. The color wheel includes three phosphorcontaining regions for converting UV light to blue light, UV light togreen light, and UV light and to red light, respectively. In operation,the color wheel emits blue, green, and red light from the phosphorcontaining regions in sequence. The blue, green and red light from thephosphor may be transmitted through the color wheel, or reflected backfrom it. In either case the blue, green, and red light is collected byoptics and redirected to the microdisplay. The UV light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.It is to be appreciated that can be other combinations of colored lightsources and color wheels thereof.

According to yet another embodiment, the present invention provides aprojection apparatus. The apparatus includes a housing having anaperture. The apparatus includes an input interface for receiving one ormore frames of images. The apparatus includes a laser source. The lasersource includes a blue laser diode, a green laser diode, and a red laserdiode. The blue laser diode is fabricated on a nonpolar or semipolaroriented Ga-containing substrate and has a peak operation wavelength ofabout 430 to 480 nm. The green laser diode is fabricated on a nonpolaror semipolar oriented Ga-containing substrate and has a peak operationwavelength of about 490 nm to 540 nm. The red laser could be fabricatedfrom AlInGaP. The green laser diode has a wavelength of about 490 nm to540 nm. The laser source is configured produce a laser beam by comingoutputs from the blue, green, and red laser diodes. The apparatusincludes a digital light processing chip comprising three digital mirrordevices. Each of the digital mirror devices includes a plurality ofmirrors. Each of the mirrors corresponds to one or more pixels of theone or more frames of images. The color beams are respectively projectedonto the digital mirror devices. The apparatus includes a power sourceelectrically coupled to the laser sources and the digital lightprocessing chip. Many variations of this embodiment could exist, such asan embodiment where the green and blue laser diode share the samesubstrate or two or more of the different color lasers could be housedin the same packaged. In this co-packaging embodiment, the outputs fromthe blue, green, and red laser diodes would be combined into a singlebeam.

As an example, the color wheel may include phosphor material thatmodifies the color of light emitted from the light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes blue and red light sources. The color wheel includes aslot for the blue color light and a phosphor containing region forconverting blue light to green light. In operation, the blue lightsource (e.g., blue laser diode or blue LED) provides blue light throughthe slot and excites green light from the phosphor containing region;the red light source provides red light separately. The green light fromthe phosphor may be transmitted through the color wheel, or reflectedback from it. In either case the green light is collected by optics andredirected to the microdisplay. The blue light passed through the slotis also directed to the microdisplay. The blue light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.Alternatively, a green laser diode may be used, instead of a blue laserdiode with phosphor, to emit green light. It is to be appreciated thatcan be other combinations of colored light sources and color wheelsthereof.

As another example, the color wheel may include multiple phosphormaterials. For example, the color wheel may include both green and redphosphors in combination with a blue light source. In a specificembodiment, the color wheel includes multiple regions, each of theregions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a blue light source. The color wheel includes a slot forthe blue laser light and two phosphor containing regions for convertingblue light to green light, and blue light and to red light,respectively. In operation, the blue light source (e.g., blue laserdiode or blue LED) provides blue light through the slot and excitesgreen light and red light from the phosphor containing regions. Thegreen and red light from the phosphor may be transmitted through thecolor wheel, or reflected back from it. In either case the green and redlight is collected by optics and redirected to the microdisplay. Theblue light source may be a laser diode or LED fabricated on non-polar orsemi-polar oriented GaN. It is to be appreciated that can be othercombinations of colored light sources and color wheels thereof.

As another example, the color wheel may include blue, green, and redphosphor materials. For example, the color wheel may include blue, greenand red phosphors in combination with a ultra-violet (UV) light source.In a specific embodiment, color wheel includes multiple regions, each ofthe regions corresponding to a specific color (e.g., red, green, blue,etc.). In an exemplary embodiment, a projector includes a light sourcethat includes a UV light source. The color wheel includes three phosphorcontaining regions for converting UV light to blue light, UV light togreen light, and UV light and to red light, respectively. In operation,the color wheel emits blue, green, and red light from the phosphorcontaining regions in sequence. The blue, green and red light from thephosphor may be transmitted through the color wheel, or reflected backfrom it. In either case the blue, green, and red light is collected byoptics and redirected to the microdisplay. The UV light source may be alaser diode or LED fabricated on non-polar or semi-polar oriented GaN.It is to be appreciated that can be other combinations of colored lightsources and color wheels thereof. Further details can be found In U.S.Pat. No. 8,427,590, which is incorporated by reference in its entirety.

In one embodiment, one or more of the user input structures areconfigured to control the device, such as by controlling a mode ofoperation, an output level, an output type, etc. For instance, the userinput structures may include a button to turn the device on or off.Further the user input structures may allow a user to interact with theuser interface on the display. Embodiments of the portable electronicdevice may include any number of user input structures, includingbuttons, switches, a control pad, a scroll wheel, or any other suitableinput structures. The user input structures may work with the userinterface displayed on the device to control functions of the deviceand/or any interfaces or devices connected to or used by the device. Forexample, the user input structures may allow a user to navigate adisplayed user interface or to return such a displayed user interface toa default or home screen.

The exemplary device may also include various input and output ports toallow connection of additional devices. For example, a port may be aheadphone jack that provides for the connection of headphones.Additionally, a port may have both input/output capabilities to providefor connection of a headset (e.g., a headphone and microphonecombination). Embodiments of the present invention may include anynumber of input and/or output ports, such as headphone and headsetjacks, universal serial bus (USB) ports, IEEE-1394 ports, and AC and/orDC power connectors. Further, the device may use the input and outputports to connect to and send or receive data with any other device, suchas other portable electronic devices, personal computers, printers, orthe like. For example, in one embodiment, the device may connect to apersonal computer via an IEEE-1394 connection to send and receive datafiles, such as media files. Further details of the device can be foundin U.S. Pat. No. 8,294,730, assigned to Apple, Inc.

As used herein, the term GaN substrate is associated with GroupIII-nitride based materials including GaN, InGaN, AlGaN, or other GroupIII containing alloys or compositions that are used as startingmaterials. Such starting materials include polar GaN substrates (i.e.,substrate where the largest area surface is nominally an (h k l) planewherein h=k=0, and l is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k l) plane wherein l=0, and at least oneof h and k is non-zero) or semi-polar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k l) plane wherein l=0, and atleast one of h and k is non-zero).

As shown, the present device can be enclosed in a suitable package. Suchpackage can include those such as in TO-38 and TO-56 headers. Othersuitable package designs and methods can also exist, such as TO-9 orflat packs where fiber optic coupling is required and even non-standardpackaging. In a specific embodiment, the present device can beimplemented in a co-packaging configuration such as those described inU.S. Publication No. 2010/0302464, which is incorporated by reference inits entirety.

In other embodiments, the present laser device can be configured in avariety of applications. Such applications include laser displays,metrology, communications, health care and surgery, informationtechnology, and others. As an example, the present laser device can beprovided in a laser display such as those described in U.S. PublicationNo. 2010/0302464, which is incorporated by reference in its entirety.Additionally, the present laser device can also include elements ofco-pending U.S. Provisional Application No. 61/889,955 filed on Oct. 11,2013, which is incorporated by reference in its entirety.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. As used herein, the term “substrate” can mean the bulksubstrate or can include overlying growth structures such as a galliumand nitrogen containing epitaxial region, or functional regions such asn-type GaN, combinations, and the like. Additionally, the examplesillustrates two waveguide structures in normal configurations, there canbe variations, e.g., other angles and polarizations. For semi-polar, thepresent method and structure includes a stripe oriented perpendicular tothe c-axis, an in-plane polarized mode is not an Eigen-mode of thewaveguide. The polarization rotates to elliptic (if the crystal angle isnot exactly 45 degrees, in that special case the polarization wouldrotate but be linear, like in a half-wave plate). The polarization willof course not rotate toward the propagation direction, which has nointeraction with the Al band. The length of the a-axis stripe determineswhich polarization comes out at the next mirror. Although theembodiments above have been described in terms of a laser diode, themethods and device structures can also be applied to any light emittingdiode device. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

What is claimed is:
 1. A method for fabricating a laser diode devicecomprising: providing a gallium and nitrogen containing substrate membercomprising a surface region; forming a patterned dielectric materialoverlying the surface region to expose a portion of the surface regionwithin a vicinity of an recessed region of the patterned dielectricmaterial and maintaining an upper portion of the patterned dielectricmaterial overlying covered portions of the surface region; performing alateral epitaxial growth overlying the exposed portion of the surfaceregion to fill the recessed region overlying the exposed portion andcausing a thickness of the lateral epitaxial growth to be formedoverlying the upper portion of the patterned dielectric material;forming an n-type gallium and nitrogen containing material overlying thedielectric material; forming an active region overlying the n-typegallium and nitrogen containing material; forming a p-type gallium andnitrogen containing material; forming a waveguide structure in thep-type gallium and nitrogen containing material; and forming atransparent conductive oxide material overlying an exposed portion ofthe p-type gallium and nitrogen containing material such that activeregion is configured between the transparent dielectric material and theconductive oxide material to cause an optical guiding effect within theactive region.
 2. The method of claim 1, wherein the transparentconductive oxide is comprised of indium tin oxide or zinc oxide; whereinthe dielectric material is comprised of silicon oxide or siliconnitride.
 3. The method of claim 1, wherein surface region of the galliumand nitrogen containing substrate is configured in a semipolar, polar,or non-polar orientation; wherein the active region comprises aplurality of quantum well regions.